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Abstract

The polyculture of tiger shrimp (Penaeus monodon) with milkfish (Chanos chanos) has been practiced in the Philippines, bit little is known about the possible polyculture of the shrimp with the tilapias in spite of increasing consumer acceptance for tilapias in the country. Shrimp monoculture, two rates of Oreochromis niloticus monoculture, and two polyculture treatments were compared for economic feasibility. The stocking combination of 6,000 ha-1 shrimp with 4,000 ha-1 tilapia generated the highest total production and net income with 283.57 kg ha-1 and P11,849 ha-1, respectively. Two crops per year provided a 70% return on investment and 1.2 years payback. A sensitivity analysis indicated that shrimp polyculture with tilapia is profitable up to a 20% decrease in the selling price of both species.

The aquaculture sector of the Philippine fishing industry registered the highest growth rate of 12.5% in 1977-1986. The contribution of aquaculture to the total fish production was equivalent to 24% in 1986 compared to only 85 in the early 1970's. In terms of quantity, the mariculture subsector registered the highest growth rate of 10.2% in 1982-1986, whereas in terms of value the brackishwater fishpond subsector showed the highest growth rate of 33%. Meanwhile, freshwater aquaculture production exhibited a negative growth rate due to reduction of activities in Laguna de Bay and the slow expansion in hectarage of the commercial freshwater fishponds.

Malaysia is a fish-consuming country with fish representing 60% of a total animal protein intake. At an annual per capita consumption of 32 kg some 560 000 mt of fish is required for the projected of 17.5 million people in year 2000.

Coastal marine capture fisheries, the mainstay of Malaysia's fishsupply, has not shown any increase in landings over the last few years. In fact in 1985 there was a decline of 3.7% compared to 1984 fish landings. This declining contribution of marine fisheries is compensated by an increase in aquaculture production. In 1985, aquaculture contributed 51 709 mt to the total fish supply. This represents 10% of the total fish landings of 514 570 mt or 13% of total table (edible) fish landings.

Malaysia does not have a long standing aquaculture tradition unlike its neighbours in the Indo-Pacific. Even then, the industry has seen rapid growth in the last few years. Today there are 19 species of finfishes, crustaceans and shellfish cultured in the country. The main freshwater fish species bred and cultured are bighead carp (Aristichthys nobilis), grass carp (Ctenopharyngodon idella), common carp (Cyprinus carpio), Indonesian carp (Punctius gonionotus), catfish (Clarias macrocephalus and Pangasius spp), snakefish gourami (Trichogaster pectoralis) and tilapia (mainly Oreochromis niloticus). Marine finfishes bred and cultured are sea bass (Lates calcarifer), grouper (Epinephelus sp.) and snapper (Lutjanus johni). Penaeus monodon is the dominant marine prawn species bred and cultured but culture of P. merguiensis is receiving considerable interest. Macrobrachium rosenbergii is the only freshwater prawn cultured commercially. Molluscs cultured are the blood clam (Anadara granosa) and the green mussel (Perna viridis).

Aquaculture in Malaysia has considerable growth potential. It is projected that 22 000 ha of mangrove will be opened by the year 2000 for shrimp culture. Some 330 000 m2 of protected coastal waters have been identified for cage culture. Some 6500 rafts can considerably expand the present capacity. In freshwater culture about 8000 ha of land and 17 500 ha of mining pools can be developed while 200 000 ha of artificial lakes and impoundments for freshwater fish cage culture are available. Yet such development is not without constraints. Freshwater finfish culture is hampered by lack of good quality broodstock. There is also a limited market for freshwater finfishes. Marine finfish culture is limited by lack of fingerlings and good quality compounded diet to replace trash fish which is deteriorating in quality and quantity. Marine prawn culture is heavily dependent on wild spawners, the supply unpredictable and inadequate. Acid sulfate soil continues to cause the deterioration of brackishwater ponds. Cockles and mussels can be sold to export markets only if they meet specific quality standards.

Aquaculture practised in Thailand is in the form of pond culture and cage culture in freshwater, brackishwater and coastal areas. The main species cultured include freshwater prawns, brackishwater shrimp, cockles, mussels, and various freshwater and marine finfishes. There is good potential for increased production from freshwater, brackishwater and marine aquaculture. However, the 1983 production of 145 000 mt represents only about 6% of Thailand's total fish production and production in this subsector has fluctuated widely. It will be several years before aquaculture production will contribute substantially to total production. Nonetheless, the culture of high value species of shrimp and fish could contribute significantly to export earnings during the next 5 to 10 years.

Conducted primarily by government agencies, research and development are along the lines of increasing seed supply, establishing new culture techniques or improving older ones. The Department of Fisheries (DOF) together with some private companies have ventured into the development and testing of artificial diets for the various cultured species using a variety of indigenous feed stuffs.

It is estimated that with adequate investments and appropriate support, aquaculture production will increase from 145 000 mt in 1983 to 378 000 mt in 1991, showing an annual increase of about 13% over this period. Major increases would come from bivalve mariculture (131 000 mt), brackishwater ponds (36 000 mt) freshwater ponds (46 000 mt) and brackishwater cage culture (20 000 mt).